Sodium Chloride and the Growth of Desulphovibrio desulphuricans

SUMMARY: The effect of sodium chloride on the multiplication of four fresh-water and three salt-water strains of sulphate-reducing bacteria was examined by determining the numbers of organisms in a known population which were viable in media of unfamiliar NaCl concentrations. The salt-water strains all produced vari-ants viable a t high NaCl concentrations; a population able to multiply in 1 Yo-10 yo NaCl was obtained by ‘training ’ one salt-water strain. They differed, however, in the frequency with which non-exacting variants appeared, ranging from a strain in which the whole population grew with 0.25 yo NaCl to one which would not grow with less than 045 yo NaCl even after repeated attempts a t acclimatization. Re-placement experiments indicated that the exigent strain required chloride ion; a less-exacting strain required sodium ion. The fresh-water strains produced few variants viable a t NaCl concentrations above 3y0, but one strain produced variants of the salt-water type after ‘training ’ to grow with 4 yo NaCl; sodium ion was mainly responsible for the inhibition of this strain by high NaCl concentrations. We con-clude that the differences among the salt- and fresh-water strains of Desulpho